Why the energy of electromagnetic waves is directly proportional to frequency whilst for mechanical waves this is not true?

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Guadalupe Reid · Accepted Answer

The difference isn&#039;t electromagnetic versus mechanical. All classical waves behave the same way, as do all quanta. The difference arises because you&#039;re treating the light as quantum and the mechanical wave as classical.The energy of a single quantum is always proportional to   ω. This is true for photons, but it&#039;s also true for the quantized excitations that make up, say, classical waves on a string.For any wave described by a generalized coordinate   ϕ  (  t  ) obeying the ideal wave equation and with standard normalization, the energy density of a classical plane wave at fixed amplitude is always proportional to       ω    2  . This is true for both classical waves on a string (where the coordinate is the height   y  (  x  ,  t  )) and for electromagnetic waves (where the coordinate is the vector potential       A    (      x    ,  t  )Combining these two results shows that the density of quanta making up a classical ideal plane wave of fixed amplitude and frequency   ω is proportional to   ω

Why the energy of electromagnetic waves is directly proportional to frequency whilst for mechanical waves this is not true?

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